/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    https://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 */
package org.grails.encoder.impl;

import org.codehaus.groovy.runtime.StringGroovyMethods;

import org.springframework.util.ClassUtils;

import org.grails.encoder.AbstractCharReplacementEncoder;
import org.grails.encoder.CodecIdentifier;
import org.grails.encoder.DefaultCodecIdentifier;

/**
 * Escapes characters in JSON output
 *
 * @author Lari Hotari
 * @since 2.3.4
 */
public class BasicJSONEncoder extends AbstractCharReplacementEncoder {
    public static final CodecIdentifier JSON_CODEC_IDENTIFIER = new DefaultCodecIdentifier(
            "JSON", "Json") {
        public boolean isEquivalent(CodecIdentifier other) {
            return super.isEquivalent(other) || JavaScriptEncoder.JAVASCRIPT_CODEC_IDENTIFIER.getCodecName().equals(other.getCodecName());
        }
    };

    public BasicJSONEncoder() {
        super(JSON_CODEC_IDENTIFIER);
    }

    /* (non-Javadoc)
     * @see AbstractCharReplacementEncoder#escapeCharacter(char, char)
     */
    @Override
    protected String escapeCharacter(char ch, char previousChar) {
        switch (ch) {
            case '"':
                return "\\\"";
            case '\\':
                return "\\\\";
            case '\t':
                return "\\t";
            case '\n':
                return "\\n";
            case '\r':
                return "\\r";
            case '\f':
                return "\\f";
            case '\b':
                return "\\b";
            case '\u000B': // vertical tab: http://bclary.com/2004/11/07/#a-7.8.4
                return "\\u000B";
            case '\u2028':
                return "\\u2028"; // Line separator
            case '\u2029':
                return "\\u2029"; // Paragraph separator
            case '/':
                // preserve special handling that exists in JSONObject.quote to improve security if JSON is embedded in HTML document
                // prevents outputting "</" gets outputted with unicode escaping for the slash
                if (previousChar == '<') {
                    return "\\u002f";
                }
                break;
        }
        if (ch < ' ') {
            // escape all other control characters
            return "\\u" + StringGroovyMethods.padLeft(Integer.toHexString(ch), 4, "0");
        }
        return null;
    }

    @Override
    public boolean isApplyToSafelyEncoded() {
        return true;
    }

    @Override
    public final Object encode(Object o) {
        return doEncode(o);
    }

    protected Object doEncode(Object o) {
        if (o == null) {
            return null;
        }
        if (o instanceof CharSequence || ClassUtils.isPrimitiveOrWrapper(o.getClass())) {
            return super.encode(o);
        } else {
            return encodeAsJsonObject(o);
        }
    }

    protected Object encodeAsJsonObject(Object o) {
        return o;
    }
}
